Barrier walls that are formed from a plurality of elongated, vertically oriented piles typically are driven into the earth to a depth sufficient to support the piles in an upright attitude. In some cases, the piles are formed with male and female opposed edges so that similar sheet piles can be locked together at their adjacent side edges to form a continuous barrier or “cutoff” wall for blocking water transport across the wall. Because of the strength required of the sheet piles when being driven into the earth and the strength required under load conditions, the sheet piles have typically been made of steel or aluminum. Frequently, steel and aluminum sheet piles have over-sized cross sections to allow for the effects of corrosion. The additional material used in “over-sizing” increases the costs of the sheet piles due to the material itself, as well as the costs associated with handling the heavier piles.
In recent years, sheet piles have been constructed of polyvinyl chloride and other plastics having relatively low structural strength. The sheet piles are extruded in a continuous manufacturing process. In order to provide the strengths in the sheet piles necessary to withstand the loads that are expected to be applied to the sheet piles, such as while being driven vertically into the earth, the thicknesses of the sheet piles have been increased over the typical thickness of similar sheet piles formed of steel or aluminum. Further increases in the thickness of the plastic provides a diminishing return. The increased bending strength does not offset the cost of the additional plastic.
In order to produce sheet piles formed of a synthetic material that are to be used as driven piles in the formation of a barrier wall, the sheet piles have often been formed in various strengthening cross-sectional shapes, such as V-shapes, Z-shapes, U-shapes, etc., that provide resistance to bending in response to the application of axial and/or lateral loads to the sheet piles. Further, the panels have been constructed so as to have at their opposite edges male and female locking elements, so that the edge of one pile locks with and supports the edge of an adjacent pile.
After the first sheet piles have been driven into place, subsequent sheet piles can be driven into place adjacent the previously driven sheet piles with their male and female edges locked together as they are driven, thereby forming a continuous barrier wall. The barrier wall typically is held in place with a series of horizontally placed structural members, or wales, that extend along the exposed outer surface of the barrier wall. The wales frequently are held in place with a plurality of tie rods. The tie rods extend through the wale, the barrier wall, and the soil disposed behind the barrier wall, and have one end secured to the wale and another end which is secured to a force abutter. Typically, the force abutter is a reinforced cement wall disposed a desired distance behind the barrier wall such that adequate force is exerted from the force abutter through the tie rods on the barrier wall, thereby maintaining the barrier wall in the desired position.
As previously noted, although measures can be taken to increase the ability of extruded plastic sheet piles to withstand the large axial loads applied during driving operations, it is not uncommon to damage sheet piles during driving operations. Miscalculations and/or misjudgments related to the required thickness of the sheet piles, or simple over application of driving force, can cause the sheet piles to be damaged. Removal and replacement of the damaged sheet piles is costly in both time and materials.
As well, warpage, twisting, deflection, etc., of a structural panel during driving operations can cause the male and female locked edges to separate between adjacent sheet piles. If the separation is detected, once again, the sheet pile must be removed and re-driven or replaced. If the separation goes undetected, the structural integrity of the barrier wall can be severely compromised. This is especially harmful where the barrier wall is being used to prevent the spread of potentially harmful liquids, such as when used on industrial facilities, around garbage dumps, during the clean up of polluted areas, etc.
U.S. Pat. No. 7,056,066 discloses an apparatus and method for inserting sheet piles into a soil formation. U.S. Pat. No. 7,056,066 is incorporated herein by reference in its entirety.
It is to the provision of an improved sheet pile and installation apparatus and related methods that the present invention is primarily directed.